THE WZZ (CLD) PROTEIN IN ESCHERICHIA-COLI - AMINO-ACID-SEQUENCE VARIATION DETERMINES O-ANTIGEN CHAIN-LENGTH SPECIFICITY

The O antigen is a polymer with a repeated unit. The chain length in m ost Escherichia colt strains has a modal value of 10 to 18 O units, bu t other strains have higher or lower modal values. wzz (cld/rol) mutan ts have a random chain length distribution, showing that the modal dis tribution is determined by the Wzz protein. Cloned wzz genes from Lt c olt strains with short (7 to 16), intermediate (10 to 18), and long (1 6 to 25) modal chain lengths were transferred to a model system, and t heir effects on 0111 antigen mere studied, The 0111 chain length close ly resembled that of the parent strains. We present data based on the construction of chimeric wzz genes and site-directed mutagenesis of th e wzz gene to show that the modal value of O-antigen chain length of E . coli O1, O2, O7, and O157 strains can be changed by specific amino a cid substitutions in wzz. It is concluded that the O-antigen chain len gth heterogeneity in E. coli strains is the result of amino acid seque nce variation of the Wzz protein.